Apparatus for changing electrical variations to mechanical



Aprill4', 1925.

K. RAHBEK ET AL APPARATUS FOR CHANGING ELECTRICAL VARIATIONS TO MECHANICAL Filed March 10. 1919" Ey agi @.51

MII Il Hill Patented Apr. 14, 19.25.

KNUD RAHBEK AND FREDERIK ALFRED JOHNSEN, OF COPENHAGEN, DENMARK.

AIPABATUS FOB CHANGING ELECTRICAL VARIATIONS TO MECHANICAL.

Application led March 10, 1919.- Serial No. 281,755.

To all lwhom it may concern.'

, Be it known that we, KNUD RAHBEK and FREDERIK ALFRED J oHNsEN, citizens of the Kingdom of Denmark, residing at Copenhagen, Denmark, have invented new' and useful Improvements in an Apparatus for Changing Electrical Variations to Mechanical, of which the following is a specification.

This` invention relates to improved apparatus for use asa relay, oscillograph, telegraph, tele hone, automatic current or voltage-regu ator, also any other arrangements sensitive to variations of volta e in an electrical circuit. More specifical y, it relates to improvements in certain apparatus operated by electro-adhesion. As the electro-adhesion effect has only in recent times been generally described in scientific literature by ourselves and others, a short description is here given. This description is not intended to be exhaustive, but to be sufficient to assure comprehension of the specification.

If two solid conducting bodies, which are connected with the positive and the negative pole respectively of a source of electricity, are brought in contact with each other, a certain potential difference will exist between the contactin surfaces on account of the well-known p enomenon of contactresistance. The said potential difference eHect-s a certain electrical attraction between the contacting surfaces, causing the latter to adhere to each other to a certain degree. In fact, t-he bodies will exhibit a certain mechanical resistance against being separated from each other'l or being caused to slide one on the other as long as they are connected with the source of electricity, and this phenomenon is termed the electro-adhesion effect. Experience shows 'that no noticeable electro-adhesion is manifest if the potential difference between the contacting surfaces is less than about l0 volts, and generally more than 40 volts potential difference is necessary for technical applications. Itis therefore evident that electro-adhesion cannot in practice be established between two metallic bodies on account of their small contact-resistance. If, on the other hand, one of the bodies is highly insulating, it will locally assume the potential of the other contacting body, and practically the whole potential of the Source of electricity will be impressed on the insulating body and not between the contactmg surfaces, soy that the electroadhesion effect will be negligible. In practice, electro-adhesion is only established between a metal and a non-metallic body possessing an appropriate conductivity or between two bodies of the latter description which are here termed semi-conductors. Electro-adhesion between two semi-conductors is, however, not referred to in the following. Non-metallic conductors, especially those conducting electrolytically, generally exhibit a very high contact-resistance with respect to other conductors, if the contacting surfaces are dry, so that a high drop of potential (several hundred volts if desired) can be maintained at the place of contact, whereby the electro-adhesion can be brought to exceed twenty pounds per square inch of the contacting surfaces, if the latter are fitted well together, the current passing between the bodies being at the same time only a fraction of a milliampere, if suitable semi-conductors are used. We have, in apparatus operated by electro-adhesion, used both organic semiconductors, such as gelatine and various modifications of cellulose, and inorganic semi-conductors, chiefly hygroscopic stones, such as various species of slate and limestone. Where in the following specification special substances exhibiting electro-adhesion are referred to as a part of an apparatus, any other suitable substances exhibiting electro-adhesion may evidently be substituted, but electro-adhesion cannot` in practice be established between two metallic bodies on account of their small contact resistance. Where, in the following, mention is made of two elements exerting electro-adhesion on one another, one of the elements is therefore in every case supposed to be non-metallic. Two bodies in contact with each other and exhibiting electro-adhesion when connected to a source of electricity are termedI as an electroadhesion system and each of the bodies as an element of this system.

Having described the nature and the principles of electro-adhesion, We shall now describe our invention in detail with respect to apparatus capable of operating as a. relay, oscillograph, telegraph, telephone, automatic current or potential regulator and other devices sensitive to variations of electrical potentials.

Fig. 1 shows, in side elevation, a zerovoltage relay constructed in a manner similar to an ordinary condenser, x,

Fig. 2 illustrates a modified construction of the same, in side elevation,

Fig. 8 illustrates a third manner of constructing the same, inl side elevation,

Fig. 4 illustrates the apparatus constructed as a loud-speaking telephone, in side elevation, partly in section, and inserted in a telephone-circuit,

lig. 5 illustrates a modified construction of the same, in side elevation, partly in section,

Fig. 6 is a perspective view of a modified manner of constructing one detail of the same,

Fig. 7 is a third manner of constructing a loud-speaking telephone, in side elevation, partly in section, and

Fig. 8 is a diagram of connections for the same used in connection with an audion.

For the production of electro-adhesion, many organic solid substances may be used, such as animal membranes, skin, bone, casein, gelatine, pyroxyline, certain kinds of paper and wood and the like, also many kinds of minerals, for instance, slate, marble and many others. In the following description it will be supposed that two of these are used, viz: gelatine and marble, but the invention is by no means limited to the use of these two materials in particular, or to any one whatever of the materials mentioned here by way of example.

Referring to Fig. l, if the substance 1 is a plate of marble or other suitable material as described, which is mechanically connected to the metal plate or foil 3, the contactresistance being reduced to a minimum, for instance, by means of a conducting adhesive agent, and a plane metal plate 2 is placed on the other side, the device.r` may be useal as a zero-voltage relay if a force P produced by a weight or spring continually tends to move the plate 2 either in a direction parallel to the surface of the plate l or in a direction perpendicular to it. It is to be understood that the voltage which is normally impressed upon the relay must be large enough to prevent the plate 2 from being moved, but the force/P will move the plate 2 if the voltage drops below a certain value or entirely disappears. l/Ve have found that if a marble plate one centimeter thick is employed, then the plane metal plate 2 with an area of one Square decimeter will be held very forcibly to the marble plate if a potential difference of about 440 volts is applied between the plates 2l and 3, and that a force of one kilogram or more, will be necessary in order to move the plate 2 along the substance l.

Another manner of constructing a zerovoltage relay is shown in Fig. 2. The one meagre? conductive member 52 is here a stationary metal cylinder around which a band 51 of thin smooth gelatine (so-called elatinepaper) is placed, it being tightene by two weights P and p of unequal size or by springs. rllhe top surface of the gelatine is covered by tin foil, gold leaf or a similar conductive coating 53, forming the other conductive body and beine connected to one of the voltage poles, whi e the cylinder 52 is connected to the other one. As lon as a certain voltage E is present, the friction will be so large that the weights cannot move the gelatine. lf the voltage diminishes or disappears, the friction is decreased, and the gelatine slides on the cylinder 52, and the weights are then able to effect the release of a switehthe closing of a circuit or the like. lf the voltage E is for instance volts, the difference between the weights may be several kilograms, even if the contact area between the cylinder and the gelatine be only a few square centimeters. The small load p has only to weigh a few grams, so that the band is merely kept tight. The current consumption of the relay is onl at the rate of l()4 to 10G amperes. rlhe re ay may further be arranged so that also the conductor 53 is stationary and the weight l will then draw the gelatine 51 itself forward between the. two metal surfaces 52 and 53, which requires twice as large a force. 0n the other hand, the elatine may, evidently, be stationary, whi e the force actuates both of the conductors 52 and 53, which may then be. shaped as plates.

The above relay cannot automatically assume its initial position, as does a magnetic Irelay, when the voltage E returns. This may be attained by an arrangement as shown in Fig. 3, where the gelatine is laid around a cylinder kept in continuous rotation, by a motor or the like, in the direction indicated by the arrow. One end-point 4 of the gelatine is here shown attached to a strong spring 5, the other end-point 6 to a weaker spring 7 serving merely to keep the gelatine tight, although there may also be used weights as in Fig. 2. As long as the voltage 151 is present, the friction between the cylinder 52 and the gelatine 51 maintains the strong spring 5 stretched while this spring contracts' itself, when the voltage drops or disappears entirely. When the voltage appears again, the point 4 returns to its former position. The members to be operated by theJ relay may then be coupled to the point 4.

It is obvious that if there is provided a recording stylus at the point 4 (Fig. 3), the apparatus may immediately be used as a telegraph-apparatus, and if the entire arrangement is constructed so that the moving parts have a very small mass or a short period of oscillation for free oscillations, re-

Lesage? spectively, then the arrangement', when f properly damped, may be used as an oscill ture isto be used for examination of the shape of curve for an alternating voltage,

`the latter must be placed in series with a suitable direct current voltage. so that the resulting voltage, in spite of the variations, continuously remains either positive or negative and, for the sake of proportionality, the direct voltage must be considerabl lar er than the voltage variations. This addltional direct current voltage makes the apparatus a polarized relay. If the alternating voltage to be examined is low, it should be stepped up, previously, by means of a Voltage transformer.

If the strong spring 5 in Fig. 3 is replaced by a membrane provided in a sound-box, the apparatus may be used as a telephone. All the arrangements mentioned in the following relate to this specific use, although several ofthem may also be considered in case l5 of the above mentioned uses.

i0 larization Voltage.

J the membrane 16 in the sound-box 8 with The telephone currents are irst stepped up to a suitable voltage by means of a transformer, and this voltage is then placed in series with a suitable direct current po- TheJ complete arrangement is shown in Fig. 4. Here the metal coating 53 of the gelatine has its voltage su plied by way of the weak spring 7 The otlier end of the gelatine band is fastened to the horn 9. 10 is the polarization voltage source, which is shown as being adjustable. 11 is the secondary side of the telephone transformer, 12 its primary side receiving telephone currents from the microphone 13 ,J/'d the battery 14. Even quite weak telephone currents in the circuit 12, 13, 14, when a suitable transformer producing a high rate of transformation is used, may produce considerable variations of voltage on the gelatine, the ohmic resistance from the coatlng 53 through the gelatine 51 to the cylinder 52 being, for instance, one megohm or more, so that the secondary current of the transformer becomes very small. The variations in the pull of the gelatine ribbon on the diaphragm may then amount to considerable portions of a kilogram, whereby an exceedingly powerful speech may be attained. The apparatus while possessing the characteristics of a relay is, at the same time, a telephone and a telephone repeater. The energy producing the sound is taken from the motor revolving the cylinder, and not from the telephone currents. In consequence hereof, it is evident that a conversation taking place over ordinary telephone subscribers lines with an ordinary microphone and with the described apparatus as receiver will be heard considerably more loudly than the human voice, so that it may be heard distinctly and be understood even in very large rooms. It is therefore also easy to record such conversation directly on a phono-graph, dictaphone or the like. In connection with a power-current microphone an apparatus of this kind speaks more powerfully than any other heretofore known speaking apparatus. The speech is fully as natural as that of the known loud` speaking telephones, when everything is correctly dimensioned.

Instead of the sound-box shown in Fig. 4, there may be used any other known sound-producing member suitable for the purpose.

The dia hragm of the sound-box or the sound-prodiicing member, respectively, may be wholly or partly relieved from the pull originating from the polarization voltage by means of a counter-pull from a suitable not shown resilient member. Besides, there ma-y be inserted a lever system between the gelatine and the sound-producer as shown in Fig. 7.

f it is not desired to reproduce the speech directly as sound, but to record it on a phonograph cylinder or the like, the soundproducer may be replaced by a suitable scribing member. Obviously, the soundproducer may also be maintained, and the recording may then be effected by directing the sound from the telephone into a normal sound-recording apparatus.

When in a telephone apparatus of this kind the diaphragm and sound-box are replaced by one or more power-current microphones of a known kind, so that the pull from the gelatine is transmitted, in suitable manner, to the movable system of the microphones, then a very powerful telephone-relay is attained.

One condition for the telephone apparatus operatinglproperly is that the cylinder 52 as well as t e gelatine 51 must be perfectly smooth and clean. In course of time there will be formed, by wear, some dust on the friction surfaces, and this powder tends to decrease the friction and causes cracking bysounds to appear. The dust is removed from the cylinder by the brush shown in rig. 4, while the dust located on the gelatine is removed, during the rotation of the cylinder, by means of a helical groove, which is cut into the cylinder and whose edges scrape the dust away. In the groove there may, furthermore, be provided a soft woolen thread or the like, which directly sweeps the dust away.

During the reproduction of powerful speech, the tightly strung elatine ribbon will have a tendency to per orm individual oscillations. These may be damped by contact with sound-dampening substances such ascotton, felt or the like.

The mechanical strength of the gelatine ribbon may be increased by`means of a paper strip or the like glued thereto.

The polarization voltage which is ordinarily between 25 and 220 volts may be taken as a fractional part of the public suply voltage, a nen direct current is available. gince a direct current voltage supplied from a central station is never entirely free from undulations due to commutation it will produce, more or less strongly a tone in the telephone. The polarization voltage should therefore, preferably, be taken from a suitable capacity, for instance one of one microfarad, connected through a suitable large resistance or self-induotance to the public supply. If direct current from a central station is not available, the polarization voltage may be produced by means of a battery of relatively small dry-cells.

It the friction is too small on account of the cylinder or the gelatine having become greasy or the like, a cleaning of both with alcohol will restore the friction to its normal value.

In order to secure a constant basic friction, the polarization voltage may be maintained constant and, instead of regulating the same as mentioned above, the effective frictional area may be varied. By this reg- .ulating method, a perfectly constant intensity of speech .may'be attained. The variation of the area may be effected by the same moving members which were used, in the above mentioned arrangement, for governing the voltage divider. The area variation itself may either be attained by the gelatine enveloping a largeror smaller sector of the cylinder or by the gelatine being coated by metal only on a portion of its length, so that a longitudinal motion of the gelatine strip will alter the eliicient frictional area.V One manner of constructing the vdevice according to this last mentioned method is shown, by way of example, in Fig. 5. The sound-box is here provided on a tube 18 pivoted about the axis 19 and in firm connection with a lever 20 tted with an adjustable weight 21 tending constantly to tilt the sound-box to the left in Fig. 5, which tendency is counteracted by the pull of the gelatine ribbon. The conductive coating of the gelatine extends only to the point 22. From the pivoted tube there extends, at right angle to the plane of the paper, a stationary tube to the horn 9. When the friction is increased for some reason or other, the sound-box 8 will be pulled to the right. Thus a portion of the metal coated area in contact with the cylinder is decreased, and the friction decreasesagain, until equilibrium is reestablished by means of the weight 21. The opposite eiect is produced during a casual decrease of the friction. By adjustment of the weight 21, the

sound-intensity of the telephone maj.' be varied as desired..

A third manner of varying the area may be attained, as shown in Fig. 6, by dividing the cylinder`A 52 into a conducting and an insulating half, 23 and 24 respectively, and by making the cylinder movable along its axis. The metal coated area of thegclatine is in contact with both halves of the cylinder, and it is evident then that an axial motion of the cylinder will cause a variation in the active frictional area. The said motion of the cylinder may be effected by one of the moving members mentioned above in connection with regulation of the voltage Y divider.

In general, any other arrangement performing the above mentioned area-regulation may be used. i

ln all the systems of regulation mentioned, the oscillations of the regulator may be damped by means of arrangements of known nature.

The telephone may be given a substantially dii'erent construction by using, instead of a rotary cylinder, a rotary disc 62 Figure 7). The gelatine 61 is then preferably fastened to a light rod 26, which is secured toa sleeve 40 on a lever 27 pivoted at 4l on a sound-box 42 and connected at one end to a diaphragm 16. The rod 26 with the gelatine attached thereto may then be arranged in such manner, that it may be easily renewable. The apparatus acquires thereby a very great similarity to a gramophone or athephone and, after a few slight modifications, it may be used as such. When the dise 62 is-rotated the gelatine 61 slides upon the upper surface of the same thus being actuated by a pull due to the. friction between the disc 62 and the gelatine. The telephone current, passing over the members 62, 61 and 63 causes an alteration in the static attraction between the members 62 and 61, thereb causing corresponding alteration in the riction and thus in the said pull, actuating the lever 27 and thereby the membrane 16.

Instead of a metal Cylinder or metal disc rotating while the gelatine with its metal coating is kept stationary there may, obviously, also be provided a rotary gelatine coated cylinder, while a stationary metal strip or stripof metallized paper or the like slides thereon.

In the foregoing it is supposed that the pressure-conducting element having the slight conductivity is made of a flexible material viz: gelat-ine. Now instead of gelatine, other materials having a slight conductivity may be used, for example, marble, slate, agate, flint, animal membranes, skin, or other organic or inorganic substances, and the arrangement of said elements varied at will, without the exercise of invention.

As the telephone here described operates, according to the principle underlying the same, with telephone-currents of rather high voltage, it will be eminently suitable for use in connection with an audion or some other similar reinforcing relay, as the intensitied telephone energy ordinarily is produced from these a )paratusesI with a rather high voltage, which may thus be used directly for this telephone without any further transforming.

Fig. 8 shows by way of example a diagram of connections for an arrangement of this nature. 28 is a circuit, including a microphone 13, a battery 14 and the primary side 12 of a telephone-transformer, the secondary side 11 of which is inserted in a circuit, including in series a direct current source 31, the secondary side 11 ot' said transformer, an audion or thermionic tube 29, an apparatus according to Fig. 4, comprising a rotary clamping member 5 2, and a stationary clamping member 53 being associated with a. telephone 16, 9 is connected in parallel to an inductance coil 30, which is inserted between the plate or anode 82 of the audion and the current source 31.

80 is the filament of the thermionic tube or audion 29 and 81 is the grid of said tube, being connected to the secondary side 11 of the tele-phone transformer 11, 12.

The current source 31 polarizes the apparatus 52, 53. The polarization Acircuit includes the source 31, the lines 92 and 35, the apparatus 53, 52 and the line 91, the inductance coil 30 and the line 93.

In order to enable a regulation of the polarization voltage between the members 52 and 53 to be. effected, there may be ininserted, in parallel to the current source 31, a large ohmic resistance 32, and the line 35 may then consist in part of a movable arm, which may slide along said ohmic resistance. 'lhe value of the voltage-difference between the lines 35 and 93, and thereby the polarization-voltage between the members 52 and 53 will consequently be higher if the distance of the said movable arm 35 from the right end of the ohmic resistance 32 is increased.

ln order to damp any oscillations in the voltage from the voltage source 31, there is inserted a capacity 34 between the lines 93 and When any electric oscillations, for instance microphonic currents, arise in the eircuit 28, said oscillations will be transmitted by the primary coil 12 to the secondary coil 11 in the circuit of the thermionic tube 29.

As well known the impression of electric oscillation upon a thermionic tube causes corresponding current-oscillations to arise in the main-circuit of the thermionic-tube. Said main-circuit includes the current source 31, the lines 92 and 90, the secondary on n; tile-gna isi-,..iheranedersalhg re,-m

siistance 30 and the line 93.

The varyin current in said main-circuit causes a varying loss of voltage in the inductanee coil 30, and consequently the voltage-difference between the two ends of Said inductance coil 3() will vary in conformity to the current variations in the main-circuit of the thermionic tube, i. e. in conformity to the microphonic current impressed upon said tube from the circuit 28.

Now the potential-difference between the two clamping elements 52 and 53 infact will comprise in series the polarizationvoltage, mentioned above, and the voltage difference between the two ends of the inductance coil 30, and because the said voltage dierence varies, the potential between the elements 52 and 53 will also vary and just in conformity to the variations of said voltage difference i. e. in conformity to the microphonic current in the circuit 28. Con-v sequently the telephone 16, 9 will reproduce the sounds, which have caused the said microphonic currents to raise, exactly in the Iiannr set forth above with respect to y one end point 4 of the gelatine ribbon bein connected to acurrent or voltageregu ating device of suitable known kind, for instance a cell-switch arm or the regulating arm of a field regulating resistance, a combination of the apparatus shown in Fig. 3 and the said regulating device may serve as an automatic current or voltage-regulator for the regulation of a current or volta e, which is directly proportional to the vo tage diiferenee between the conductors 52 and 53.

Having now particularly described the nature of our. said invention and in what manner the same is to be performed, we de' clare that what we claim is:

l. A telephonie receiver comprising an electro-adhesion system having a rotary element and a non-rotary element, said elements, one of which is non-metallic sliding on one another and exerting electro-adhesion on one another, and a stationary diaphragm connected mechanically to the non-rotary element.

2. A telephonie receiver comprising an eleetro-adhesion system having a rotary element and a non-rotary element. said elements sliding on one another and exerting electro-adhesion on one another, a cleaning brush in contact with the rotary element, and a stationary diaphragm connected mechanically to the non-rotary element.

3. A telephone receivercomprising an electro-adhesion system having a rotar element and a non-rotary element, sai elements slidin on one another and exerting electro-adhesion on one another, a cleaning brush in contact with the rotary element, a

stationary diaphragm connected mechanically to the non-rotary element, and means Jfor producing alternatin telephonie currents superimposed on a direct current, said means connected across the electro-adhesion system.

4:. A telephone receiver comprising an electro-adhesion system having a rotary element and a non-rotary element, said elements slidin on one another and exerting electro-adhesion on one another, a cleaning brush in contact with the rotary element, a stationary diaphragm, connected mechanically to the non-rotary element, and means for producing alternating currents superimposed on a direct current, said means comprlsing in series an inductance coil and a direct current source, said means being connected across the electro-adhesion system.

5. A telephone receiver comprising an electro-adhesion system having a rotary element and a non-rotary element, said elements slidin onv one another and exerting electro-adhesion on one another, a cleaning brush in contact with the rotary element, a stationary diaphragm connected mechanically to the non-rotary element, and means for producing alternating currents superimposed on a direct current, said means comprising in series a transformator Winding and a direct current source, said means being connected across the electro-adhesion system.

In testimony whereof We have signed our names to this specification in the presence of two subscribing Witnesses.

KNUD RAHBEK. FREDERIK ALFRED JOHNSEN. Witnesses:

C. WUNNINGSEN, U. BANca 

